The existing low-temperature polysilicon devices are devices with extremely-fine structure and electrical properties. Each film is required to have high quality. In the prior art, a polysilicon layer is deposited on a SiO2 layer by a vapor deposition method. The polysilicon layer of the device is then crystallized. However, during the crystallization of the polysilicon layer, two adjacent grains extrude each other to form protrusions when they grow up. The larger the grains are or the more the intersecting grain boundaries are, the higher the protrusion is and the larger the surface roughness is. As a result, there would be the problems of a broken film, unclean etching, or tip discharge in the subsequent process. Accordingly, the production yield of the low-temperature polysilicon device products is reduced.